Grooved rotors for discs and clutches are known for example from WO 2004/020862 which shows the features of the preamble of claim 1, as well as from WO02/06694, JP 2017235, U.S. Pat. No. 5,671,835, U.S. Pat. No. 4,726,455, JP 10026159, JP 08145091, JP 55054733, SU 1484995, DE 2507264, JP 63259227, DE 262061, JP 62-209234, DE 198 24 465, U.S. Pat. No. 5,735,366, U.S. Pat. No. 5,176,236, U.S. Pat. No. 4,995,500, U.S. Pat. No. 4,286,694, U.S. Pat. No. 5,101,953, U.S. Pat. No. 4,379,501, U.S. Pat. No. 5,474,161, U.S. Pat. No. 5,480,007, U.S. Pat. No. 5,662,192, U.S. Pat. No. 5,765,667, U.S. Pat. No. 5,819,888, EP 0 287 017, GB 2 268 552, WO 97/43559, U.S. Pat. No. 2,144,223, U.S. Pat. No. 2,835,355, U.S. Pat. No. 3,623,577, U.S. Pat. No. 3,809,192, U.S. Pat. No. 3,972,400, U.S. Pat. No. 4,396,100, U.S. Pat. No. 4,726,455, U.S. Pat. No. 5,358,086, U.S. Pat. No. 5,682,971, FR 2,561,732, U.S. Pat. No. 2,728,421, U.S. Pat. No. 3,425,524, U.S. Pat. No. 5,671,835, U.S. Pat. No. 6,446,770, and also from the 1993 catalog “Wilwood disc brakes” (Wilwood engineering Inc.) and from the 1999 catalog Biltemakatalogen (Sweden).
Known grooved bands have a non-optimal distribution of grooves for the purposes of achieving an optimal average friction coefficient, as well as of achieving the balance of stresses on the brake pads and thus the elimination of the vibrations caused on the disc and on the brake pad by their interaction during the braking action.
In known braking bands, main rotation direction of the disc means the rotation direction corresponding to the forward travel of the vehicle.
Radial direction (R-R) indicates a direction lying on a plane perpendicular to the rotation axis (A-A) of the braking band and intersecting the rotation axis itself.
Tangential direction (T-T) indicates a direction tangent to a circumference lying on a plane perpendicular to the rotation axis of the braking band and having a point of the rotation axis itself as its center. Such a circumference defines a circumferential direction of the disc.